【Objective】 To prevent youth risk behaviors is one of the important issues in school health education. Previous studies reported some factors are related to such risk behaviors. In this study we surveyed Small Screen Time (SST) which is the amount of hours spent watching television, videos, DVDs, using the internet, PCs, or playing portable games, etc., as a relevant factor. The purposes of this study were to clarify the situation of SST and examine relationships between the prevalence of risk behaviors and SST among Japanese high school students.

【Methods】 Data of a national survey, the Japan Youth Risk Behavior Survey (JYRBS) 2011 was used for this analysis. The subjects were 9, 778 students: 5, 027 males, 4, 751 females, in the 10th to 12th grade of 102 schools randomly selected among high schools throughout Japan. In the current study, we focused on the ten items of risk behavior in JYRBS 2011: “lack of vigorous physical activity”, “skipping breakfast”, “short sleep duration”, “current cigarette use”, “current alcohol use”, “lifetime thinner use”, “ever had sexual intercourse”, “rarely or never wore seatbelts”, “in a physical fight”, and “seriously considered attempting suicide”. Length of SST was the number of hours spent on SST activities on the school day before the survey.

【Results】 Regarding the length of SST, 30.9% of males and 27.0% of females answered “less than 2 hours”, 39.4% of males and 39.6% of females answered “2 hours or more and less than 4 hours”, 17.2% of males and 20.6% of females answered “4 hours or more and less than 6 hours”, and 12.0% of males and 12.6% of females answered “6 hours or more”. Prevalence rates of many risk behaviors among students whose SST was four hours or more are significantly higher than those of students whose SST was less than four hours. In particular, for the group of “6 hours or more”, the prevalence rates of most risk behaviors are significantly high. Furthermore, the group of longer SST tended to engage in more Multiple Risk Behaviors (MRB).

【Conclusion】 It was shown that the situation of SST among Japanese high school students is concerning and long SST is related to the prevalence of risk behaviors. Especially, it was found that spending more than four hours of SST a day might lead to these behaviors. This suggests that restraining SST among adolescents is important for preventing risk behaviors.